When animating the movement of a UIView within a begin / commit animation block, you can use the following method to set the animation timing curve:

[UIView setAnimationCurve:UIViewAnimationCurveEaseInOut];
When animating a layer via CAAnimation, you can use the following to set the timing function there:

[animation setTimingFunction:kCAMediaTimingFunctionEaseInEaseOut];
Finally, when wrapping a series of animations in a CATransaction, you can use the following to set the coordinated timing function of all the animations:

[layer addAnimation:move forKey:@"position"]; // Replaces the previous position animation on the layer
[layer setPosition:CGPointMake(xPos, yPos)]; // Sets the final position after animation is finished